Apparatus for stripping insulation from stranded electrical cable

ABSTRACT

Insulation is stripped from a multiple wire strand electrical cable by urging a pair of opposed, heated stripping blades having blunt edges against the cable insulation to thermally deteriorate the insulation, rotating the stripping blades, and pulling the cable in a longitudinal direction away from the stripping blades. The heated stripping blades penetrate the insulation but are sufficiently blunt so that they do not nick the wire strands of the cable.

0 United States Patent 1151 3,636,799 Weitala et al. 45 Jan, 25, 1972APPARATUS FOR STRIPPING 1,595,799 8/1926 Massingham ..8 1/951 INSULATIONFROM STRANDED 2,393,919 1/1946 Lucarelle et al. "8 l/9.5l ELECTRICALCABLE FOREIGN PATENTS OR APPLICATIONS [721 Invent: 'l Wm Allis; P386,568 1 1933 Great Britain ..8l/9.5l

Anderson, Milwaukee, both of W1s.

[73] Assignee: Allis-Chalmers Manufacturing Company, Primary Condo"Milwaukee, Wis Assistant Examiner-Roscoe V. Parker, Jr.

Aztorney-Lee H. Kaiser, Robert B. Benson and Thomas F. [22] Filed: Mar.3, 1970 Kirby [21] AppLNo: 16,190 A'STRACT [52} Insulation is strippedfrom a multiple wire strand clccuienl 5| 1 cable by urging a pair ofopposed, heated stripping blades hav- [58] ing blunt edges against thecable insulation to thermally 219/68 deteriorate the insulation,rotating the stripping blades, and pulling the cable in a longitudinaldirection away from the stripping blades. The heated stripping bladespenetrate the in- [56] References cued sulation but are sufficientlyblunt so that they do not nick the UNITED STATES PATENTS wire strands ofthe cable.

1,3 5l,l8 8029 Nelson ..8 l 5 Claims, 6 Drawing Figures PATENIEU JANZS1972 SHEET 2 BF 3 M 4 WW Hi APPARATUS FOR STRIPPING INSULATION FROMSTRANDED ELECTRICAL CABLE This invention relates to apparatus forstripping insulation from electrical cable and in particular to suchapparatus for stripping insulation from multiple wire strand cable.

Apparatus having opposed knife blades for severing insulation andstripping the severed length of insulation from an electrical cable iswell known, but such apparatus is generally unsatisfactory for multiplewire strand electrical cable covered with the tough plastic insulationsuch as polyvinyl chloride and cross-linked polyethylene which have hightensile strength. Such insulation often has an irregular wall thicknessand extends between the wire strands on the outer periphery of thecable, and when knife blades are used to penetrate and strip theinsulation, the knife blades frequently nick the wire strands with theconsequence that the strands are easily broken in use.

It is an object of the invention to provide an improved method andapparatus for stripping insulation from multiple strand cable.

This and other objects and advantages of the invention will be moreeasily understood from the following detailed description whenconsidered in conjunction with the accompanying drawing wherein:

FIGS. 1, 2, 3 and 5 are elevation, plan, left end and right end viewsrespectively of a preferred embodiment of the invention, FIG. 1 beingpartly in section;

FIG. 4 is a view taken along FIG. IV-IV of FIG. I; and

FIG. 6 is a view taken along FIG. VI-Vl of FIG. 5.

Referring to the drawing, a preferred embodiment of the invention has agenerally rectangular base 10 and a flat movable table 11 supported onand reciprocable longitudinally of base 10 within inverted L-shapedguides 12 secured by suitable means to the sides of base 10. A length ofcable 14 having a multiple wire strand conductor 15 covered by thermallydeteriorable, or degradable insulation 16 may be rigidly held on movabletable 11 by suitable clamping means of the bench clamp type shown ashaving spaced-apart elongated members 17 bolted to table 11 and providedwith sloping sides 18 (see FIG. 3) between which cable 14 is disposedand an inverted V- shaped jaw 19 movable toward and away from table 11by a manually operated toggle mechanism 20 to grip cable 14 at fourpoints about its periphery. When handle 21 of toggle mechanism 20 islifted upwardly, V-shaped jaw 19 is raised from table 11 to releasecable 14.

Table 11 may be moved longitudinally of base 10 by an air cylinder 22secured to a transverse member 23 of base 10 by suitable means shown asa nut 24. The piston 25 of air cylinder 22 is secured to an L-shapedbracket 26 afiixed to the bottom surface of table 11. A source ofcompressed air available from a conduit 27 may be connected by a valve28 to a conduit 29 leading to one end of air cylinder 22 to move piston25 and table 11 longitudinally of base 10. Valve 28 may be operated by ahandle 30 to a first position wherein it supplies compressed air overconduit 29 to air cylinder 22 to move table 1 l in a direction away fromthe stripping blades and may also be actuated by handle 30 to a secondposition wherein it supplies compressed air over a conduit 31 to theother end of air cylinder 22 to retract the table II.

A circular support member, or bearing member 32 may be affixed to oneend of base 10 by suitable means such as welding so that it is disposedin a vertical plane. A flat circular blade carrier, or cutting head 33is mounted for rotation on circular support member 32 by a plurality ofarcuately spacedapart bearing rods 34 which extend through blade carrier33 adjacent its outer margin and have circumferential flanges 35 whichoverlap the edges of circular support member 32. A handle 36 is securedto cutting head 33 to permit manual rotation thereof. A fixed lowerblade support 37 is rigidly secured to blade carrier 33 with thermallyinsulating material 38 therebetween and has an axially extending recess39 adapted to receive a self-contained electrically insulated, cartridgeresistance element 40. A lower stripping blade 41 is positioned againsta radial extension 42 at the radially inner end of lower blade support37 and is releasably secured thereto by screws 43 so that blade 41 isheated by resistance element 40 when this element is energized overconductors 45 from a source of electrical power. Lower stripping blade4! may have a circular, cutout portion 48 which conforms to thecircumference of the multiple strand conductor 15 of cable 14.

A radially extending upper blade support 50 is supported on bladecarrier 33 with insulation 5l therebetween so as to be movable radiallyrelative to lower blade support 37 and is resiliently urged in aradially inward direction by a pair of compression springs 52 disposedon opposite sides of upper blade support 50. Cup-shaped members 53fitting over the radially outer end of springs 52 abut against L-shapedbrackets 54 affixed to blade carrier 33 adjacent its outer margin, andcup-shaped members 55 fitting over the radially inner end of springs 52abut against L-shaped brackets 56 affixed to upper blade support 50 sothat springs 52 urge upper blade support 50 in a radially inwarddirection. Upper blade support 50 has an axially extending recess 57adapted to receive a selfcontained, electrically insulated, cartridgeresistance element 40. A metallic upper stripping blade 58 may bepositioned against a radially inward extending portion 59 on upper bladesupport 50 and be releasably secured thereto by screws 60 so that blade58 is heated by resistance element 40 when this element is electricallyenergized over conductors 45. Upper stripping blade 58 may have acircular cutout portion 61 which conforms to the circumference of themultiple strand conductor 15 of cable 14. Adjacent its outer edges,upper stripping blade 58 may have depending, spaced-apart legs 62provided with elongated slots 63 in a vertical plane which receive theedges of lower stripping blade 41 and guide it as blades 41 and 58 arereciprocated relative to each other. The legs 62 mechanically reinforcethe lower blade 41 against the forces exerted against it when table 11is reciprocated to pull the cable 14 in a longitudinal direction awayfrom the stripping blades.

A radially extending guide slot 65 is provided through blade carrier 33.A connecting member 66 having an elongated guide portion 67 reciprocableradially within guide slot 65 is affixed to upper blade support 50 atone side of blade carrier 33 and has at the other side of blade carrier33 outwardly extending flanges which overlap blade carrier 33.

A manually operable blade separating lever 70 is fulcrumed on base 10,i.e., it is pivotally mounted between its ends on a pivot pin extendingthrough post 72 affixed to base 10 and has an actuating cam portion 74at one end extending parallel to the axis of blade carrier 33 anddisposed beneath a cam follower abutment 76 on connecting member 66. Itwill be appreciated that manual depression of the free end of lever 70will bring actuating cam portion 74 into engagement with cam followerabutment 76 and thus move connecting member 66 and upper blade support50 in a radially outward direction to separate upper and lower bladesupports 37 and 50 and thus move upper stripping blade 58 radially awayfrom fixed lower stripping blade 41.

A stop 78 may be pivotally mounted on a bracket 79 affixed to cuttinghead 33, and the end of the cable I4 is abutted against stop 78 todetermine the length of insulation 16 to be stripped. An actuating rod80 pivotally connected at one end to stop 78 at a point spaced from theaxis of rotation of stop 78 and connected at its upper end to upperblade support 50 lifts stop 78 to a position shown in dotted lines inFIG. 5 where it interferes with cable 14 when blade-separating lever 70is manually depressed to move upper blade support 50 radially outward topermit insertion of cable 14 between stripping blades 41 and 58. Whenlever 70 is released, the springs 52 move upper blade support 50radially inward and translate actuating rod 80 to pivot stop 78 downwardfrom its interfering position so that the severed length of insulation16 can fall free.

Handle 36 is affixed at one end of an elongated rod 84 that extendsthrough a clearance hole in a bracket 85 affixed to cutting head 33 andbears against upper blade support 50 to permit the operator to manuallyexert pressure radially inward against upper blade support 50 inaddition to the force provided by springs 52.

In accordance with the invention, the stripping blades 41 and 58 haveblunt, or dull edges so that they do not nick the wire strands ofconductor 15 when they are rotated relative to cable 14. For example,the edges of the blades 41 and 58 at the cutout portions 48 and 61 maybe flat and have a width approximately equal to the diameter of the wirestrands of the cable.

in operation, blade-separating lever 70 is manually depressed to moveupper stripping blade 58 away from the fixed lower blade 41, and alength of cable 14 is placed on table 11 so that one end protrudesthrough axial aperture 86 in cutting head 33 and is manually clamped totable 11 by toggle clamp 20. The cable insulation 16 rests in the cutoutportion 48 in lower blade 41, and when lever 70 is released, springs 52urge the cutout portion 61 in upper stripping blade 58 against theinsulation 16 on cable 14. The stripping blades 41 and 58 have beenheated by resistance elements 40 and urged together by springs 52 sothat they thermally deteriorate and penetrate the insulation 16 on cable14. Cutting head 33 may then be rotated manually through an angle suchas 45 in both directions from its normal position by means of handle 36.Rotation of the heated opposed blades 41 and 58 severs the insulationdown to the wire strands of conductor 15, but the blunt stripping blades41 and 58 do not nick the wire strands. Valve 28 is then actuated byhandle 30 to operate air cylinder 22 and move table ii in an axialdirection away from cutting head 33, and the cable 14 clamped on table 11 pulls against the stripping blades 41 and 58 which have penetrated andpartially severed the insulation 16 to break apart the remaining threadsof insulation between the strands which have not been parted by rotationof heated stripping blades 41 and 58. Table 11 is preferablyreciprocated through a distance equal to at least twice the length ofinsulation 16 to be stripped from cable 14 to assure that the strippedlength falls free.

Different stripping blades 41 and 58 having cutout portions 48 and 61may be substituted when it is desired to strip insulation from cable ofa different size.

Although the preferred embodiment is disclosed with a clamped cable androtating stripping blades, it will be appreciated that the invention canalso be practiced by rotating the cable relative to fixed heated bluntstripping blades. Further, although the disclosed invention finds itsprincipal utility with multiple strand cable having insulation whichdeteriorates under heat, it will be appreciated that the invention isalso operable with single strand cable and with cable having other typesof insulation such as rubber.

It should be understood that we do not intend to be limited to theparticular embodiment shown and described for many modifications andvariations thereof will be obvious to those skilled in the art.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Apparatus for stripping a length of thermally deteriorable insulationfrom a multiple wire strand cable comprising, in combination,

a pair of stripping blades having opposed, sufficiently blunt strippingedges so that they will not nick the wire strands of said cable whenpressed against and moved across said strands,

means for urging said stripping blades toward each other and against theinsulation of said cable when said cable is inserted between saidstripping edges,

means for heating said stripping blades,

means for clamping said cable in a position so that a length thereof maybe inserted between said stripping blades,

means for rotating said clamping means and said stripping bladesrelative to each other, and means for moving said clamping means andsaid stripping blades relative to each other in a direction axial ofsaid cable.

2. Apparatus for stripping a length of thermally deteriorable insulationfrom a multiple strand cable, comprising, in combination,

a rotatable stripping blade carrier,

a pair of stripping blades having sufficiently blunt stripping edges sothat they will not nick the strands of said cable when pressed againstand moved across said strands,

means for mounting said stripping blades on said rotatable carrier sothat they are movable relative to each other in a radial direction andsaid blunt edges are opposed and including resilient means for urgingsaid pair of stripping blades toward each other and against theinsulation of said multiple strand cable when it is inserted betweensaid blunt stripping edges,

means for heating at least one of said blades, and

means for clamping said cable in coaxial relation to said rotatablecarrier with a length thereof inserted between said opposed strippingblades, said means for clamping and said carrier being movable relativeto each other in a direction parallel to the axis of said cable.

3. Apparatus in accordance with claim 2 wherein said means for clampingincludes a member disposed adjacent said rotatable carrier with acable-receiving surface thereof parallel to said axis of rotation ofsaid carrier and said apparatus also includes fulcrumed lever means foroperatively engaging one of said blades and moving it in a radiallyoutward direction to separate said pair of blades.

4. Apparatus for stripping a length of thermally deteriorable insulationfrom a multiple strand cable comprising, in combination,

a base,

a circular support affixed to said base,

a stripping blade carrier rotatably mounted on said circular support,

a pair of hollow blade supports,

means for mounting said blade supports on said rotatable carrier so thatthey are movable radially relative to each other and including springmeans for resiliently urging said blade supports toward each other,

a pair of stripping blades having stripping edges each of which isaffixed to one of said blade supports so that said stripping edges areopposed, said stripping edges being sufficiently blunt so that they willnot nick the wire strands of said cable when pressed against and movedacross said strands,

resistance element means disposed in said hollow blade supports forheating said stripping blades,

lever means fulcrumed on said base selectively operable to engage one ofsaid blade supports and move it in a radially outward direction toseparate said stripping blades, and

means for clamping said cable on said base with its axis coincident withthe axis of rotation of said blade carrier and a length thereof insertedbetween said opposed stripping blades.

5. Apparatus in accordance with claim 4 wherein said means for clampingincludes a cable-supporting member mounted on and reciprocable relativeto said base with a surface parallel to said axis of rotation,

a clamp on said cable-supporting member, and

air cylinder means selectively operable to reciprocate saidcable-supporting member relative to said base in a direction parallel tosaid axis of rotation and away from said blade carrier.

1. Apparatus for stripping a length of thermally deteriorable insulationfrom a multiple wire strand cable comprising, in combination, a pair ofstripping blades having opposed, sufficiently blunt stripping edges sothat they will not nick the wire strands of said cable when pressedagainst and moved across said strands, means for urging said strippingblades toward each other and against the insulation of said cable whensaid cable is inserted between said stripping edges, means for heatingsaid stripping blades, means for clamping said cable in a position sothat a length thereof may be inserted between said stripping blades,means for rotating said clamping means and said stripping bladesrelative to each other, and means for moving said clamping means andsaid stripping blades relative to each other in a direction axial ofsaid cable.
 2. Apparatus for stripping a length of thermallydeteriorable insulation from a multiple strand cable, comprising, incombination, a rotatable stripping blade carrier, a pair of strippingblades having sufficiently blunt stripping edges so that they will notnick the strands of said cable when pressed against and moved acrosssaid strands, means for mounting said stripping blades on said rotatablecarrier so that they are movable relative to each other in a radialdirection and said blunt edges are opposed and including resilient meansfor urging said pair of stripping blades toward each other and againstthe insulation of said multiple strand cable when it is inserted betweensaid blunt stripping edges, means for heating at least one of saidblades, and means for clamping said cable in coaxial relation to saidrotatable carrier with a length thereof inserted between said opposedstripping blades, said means for clamping and said carrier being movablerelative to each other in a direction parallel to the axis of saidcable.
 3. Apparatus in accordance with claim 2 wherein said means forclamping includes a member disposed adjacent said rotatable carrier witha cable-receiving surface thereof parallel to said axis of rotation ofsaid carrier and said apparatus also includes fulcrumed lever means foroperatively engaging one of said blades and moving it in a radiallyoutward direction to separate said pair of blades.
 4. Apparatus forstripping a length of thermally deteriorable insulation from a multiplestrand cable comprising, in combination, a base, a circular supportaffixed to said base, a stripping blade carrier rotatably mounted onsaid circular support, a pair of hollow blade supports, means formounting said blade supports on said rotatable carrier so that they aremovable radially relative to each other and including spring means forresiliently urging said blade supports toward each other, a pair ofstripping blades having stripping edges each of which is affixed to oneof said blade supports so that said stripping edges are opposed, saidstripping edges being sufficiently blunt so that they will not nick thewire strands of said cable when pressed against and moved across saidstrands, resistance element means disposed in said hollow blade supportsfor heating said stripping blades, lever means fulcrumed on said baseSelectively operable to engage one of said blade supports and move it ina radially outward direction to separate said stripping blades, andmeans for clamping said cable on said base with its axis coincident withthe axis of rotation of said blade carrier and a length thereof insertedbetween said opposed stripping blades.
 5. Apparatus in accordance withclaim 4 wherein said means for clamping includes a cable-supportingmember mounted on and reciprocable relative to said base with a surfaceparallel to said axis of rotation, a clamp on said cable-supportingmember, and air cylinder means selectively operable to reciprocate saidcable-supporting member relative to said base in a direction parallel tosaid axis of rotation and away from said blade carrier.